Historic note:
originally, ST/X had separate classes for the various entry methods;
there were YesNoBox, EnterBox, InfoBox and so on.
In the meantime, the DialogBox class (and therefore its alias: Dialog)
is going to duplicate most functionality found in these classes.
In the future, those existing subclasses' functionality is going to
be moved fully into Dialog, and the subclasses will be replaced by dummy
delegators. (They will be kept for backward compatibility, though).
An EnterBox2 is like an EnterBox but with 2 action buttons.
This is used (for example) in the search-boxes, where two ok-buttons
'find-previous' and 'find-next' are needed in addition to the abort button.
The protocol is like that of EnterBox, the additional buttons label
can be set with 'okText2:aString' and its action with 'action2:aBlock'.